Large Solar Dwarf

Can life exist on the planet called Gliese 581d since it might have liquid water on its surface?

The astrophysicists refer to the "golden hair zone" which is the distance from a Sun where a planet has the amount of light needed for water not to either freeze or boil away and disappear.

an artist's impression of Earthlike planet orbiting a sun named Gliese 581. Credit: ESO

 

If this is correct, the rock planet Gliese 581d is the first alien planet found that could potentially sustain life, with similar soil characteristics such as oceans, clouds and rain, according to the study published in The Astrophysical Journal Letters , reports Space.com .

The study and the preliminary results assumes that Gliese 581d has a thick atmosphere composed of carbon dioxide (CO 2) which leads to a significant greenhouse effect. This can produce enough heat that water remains liquid. Several other studies have suggested similar conclusions.

This is speculative assumptions, as the researchers cannot conclude that the atmosphere is so, but the keep the option open until proven otherwise. It is possible for such a large planet, but not certainly, they say.

And the assumption that the planet has a thick CO 2- atmosphere is absolutely necessary. The planet receives only one third of the energy Earth receives from our sun, and it is probably a so-called bound rotation . This means that the same side always faces the sun - just like the moon does to Earth.

Thus, it is eternal day on one side, and eternal night on the other. Because of this, scientists have believed that the night side is permanently frozen, which destroys the possibility of a life-supporting climate.

The researchers behind the new study, which is associated Laboratoire de Dynamique metrology at the Institut Pierre Simon Laplace in Paris, has developed computer models to simulate the atmospheres of alien planets.

The simulations show that Gliese 581d might have liquid water on its surface, if the atmosphere is CO 2-dense. Greenhouse effects will be able to produce enough heat to maintain liquid water, and this can circulate over the night side so that it does not freeze over, according to the researchers.

It may take several years before we get a clear answer to the question. In order to determine with certainty whether Gliese 581d is actually habitable for life - as we know it - scientists must observe and analyze the atmosphere directly, which requires a new generation of advanced telescopes.

The distance of 20 light years, albeit very short compared to the big picture, is a relatively serious obstacle to a direct exploration by humans or probes. Today's spacecraft will use about 300 000 years on a mission if ever launched to reach it with todays technology.

Another planet in the solar system around Gliese 581 may be potentially habitable for life - if it exists. Gliese 581g is around three times as massive as Earth, and probably a globe made of stone (as opposed to the gas planets). It is located right in the habitable zone .

But after it was announced with great fanfare last fall, follow-up studies have yet to confirm that the planet actually exists.

The sun Gliese 581 in the Libra constellation. Credit: ESO Digitized Sky Survey

Nearby the red dwarf Gliese 581 in the constellation of Libra around which have been found six extrasolar planets, including one (Gliese 581e) that is the lightest discovered to date (only about 1.9 times the mass of Earth) and another (Gliese 581g) that is first low-mass planet found to orbit in the middle of its star's habitable zone and which could therefore support permanent liquid water on its surface. Another planet, Gliese 581d, appears to orbit at the outer edge of the habitable zone.

Gliese 581g
The discovery of Gliese 581g was announced on September 29, 2010. This is the first planet to be found orbiting more or less in the middle of its star's habitable zone, and is therefore an excellent candidate for supporting life as we know it. Gliese 581g has a 37-day orbit and a mass between 3.1 and 4.3 times that of Earth. Its relatively low mass means it is almost certainly a rocky world.

Gliese 581e
At the time its discovery was announced, on April 21, 2009, Gliese 581e had the lowest published mass of any known exoplanet, apart from a very small world orbiting a pulsar. Also, it is suspected that the exoplanet MOA-2007-BLG-192-L b, discovered by the method known as microlensing, might weigh as little as 1.4 Earth masses, though this has yet to be confirmed.

The low mass of Gliese 581e means that it is almost certainly rocky like the Earth. However, it orbits too closely to its parent star for there to be a realistic chance of it harboring any surface water.

Gliese 581d
Earlier estimates put the orbital period of planet d at 83 days, placing it outside Gliese 581's habitable zone. However, this value was revised downward to 66 days in an announcement made at the same time as that of the discovery of planet e. The new figure gives planet d an orbit lying entirely within the outer boundary of the habitable zone. The mass of 581d – 7 times that of Earth – suggests that it is not made entirely of rock, nor can it be a large gas giant like Jupiter or Saturn. Instead it may have a composition similar to that of Uranus or Neptune, with a rocky core surrounded by a deep mantle of water, ammonia, and methane. Much of this water, it has been suggested, may be in a liquid state, possibly making 581d the first of a new class of ocean planets.

About the Author

Stig-Arne Kristoffersen has a background as civil engineer and geoscientist. He has worked mainly within the oil and gas industry from the mid 1980s. He has written a few fictional novels as well as being the author of some professional litterature within oil and gas sector, he act as a writer to various web sites.

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